The U.S. military has confirmed that a U.S.-led coalition has intensified air strikes against Islamic State (IS) militants in northern Syria -- launching six attacks since October 7 near the city of Kobani on the border with Turkey.

A statement by U.S. Central Command on October 8 says the air strikes destroyed IS armed vehicles and artillery.

Reports from the ground say IS militants withdrew overnight from positions on the west side of the besieged city but were still battling from eastern and southeastern parts of Kobani on October 8.

Salih Muslim Muhammad, the leader of the Syrian Kurdish movement PYD, told RFE/RL that there was "hard, face-to-face fighting" going on in the streets of Kobani on October 8 after U.S.-led air strikes destroyed "IS tanks."

Muhammad said the air strikes have helped Kobani's Kurdish defenders, but he also said they were not enough and "should continue."

Meanwhile in Washington, Secretary of State John Kerry said the United States was "deeply concerned" about the people of Kobani.

But he added: "Horrific as it is to watch the violence, it is important to keep in mind the U.S. strategic objective," which is to deprive IS of command-and-control centers and the infrastructure to carry out attacks.

Kerry also said he expected Turkey to decide "over the next hours, days" what role it may play against the IS group.

French President Francois Hollande told Turkish President Recep Tayyip Erdogan on October 8 that he supports the idea of Turkish troops deploying on the Syrian side of the border to create a buffer zone and safe haven for civilians displaced by the fighting.

Erdogan has warned that Kobani is facing an immediate risk of falling to the IS militants.

But Turkey has so far refused to send troops into northern Syria, even though the Turkish parliament has passed a resolution authorizing such deployments if the government sees fit.

The UN envoy to Syria, Staffan de Mistura, has appealed for immediate international action to support Kobani's Syrian Kurdish defenders.

He has warned of a grave humanitarian crisis, including the risk of mass executions, if the IS militants capture the border city.

The capture of Kobani also would give IS militants control of the entire Syria-Turkey border.

In Turkey, at least 14 Kurds were killed overnight during protests against Turkey's refusal to deploy troops in Syrian territory to help defend Kobani from the IS militants' advance.

U.S. Secretary of State John Kerry has called Turkish Prime Minister Ahmet Davutoglu to discuss Ankara's reluctance to engage IS militants there.

Analysts say Ankara appears wary because Kobani's Syrian Kurds have links to Turkish Kurdish rebels who have fought for more than three decades against Turkey's military.

Elsewhere, officials in Baghdad said Islamic State militants shot down an Iraqi military helicopter near the oil refinery town of Baiji in northern Iraq, killing two pilots on board.

It was the second Iraqi military helicopter to be shot down by IS militants in the past week.

Authorities say the militants used a shoulder-fired missile to shoot down the U.S.-built Bell 407 helicopter north of Beiji on October 8.

Militants also shot down a Russian-built Mi-35 transport-assault helicopter near Baiji on October 3, killing the pilot and co-pilot.